The present invention resides generally in the field of tars and tar pitches. More specifically, the present invention relates to pitches which are useful in the production of anodes in the aluminum industry, and which have reduced levels of polyaromatic hydrocarbons (PAH's).
As further background, pitch resulting from the distillation of coal tar has long been used for many purposes. These include its use as a binder for carbon and graphite in the formation of carbon bodies and in the production of anodes, cathodes, electrodes, etc. for use in the metal industry. For example such electrodes are used in electrolytic reduction processes such as aluminium reduction.
Despite the historical use of coal tar pitch, in more recent years health concerns have been raised in connection with coal tar pitch. Coal tar contains a number of polyaromatic hydrocarbons, including anthracene, fluorene, phenanthrene, pyrene, fluoranthene, benz(a)anthracene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, benzo(e)pyrene, dibenz(a,h)anthracene, benzo(g,h,i)perylene and indeno(1,2,3,c,d,)pyrene. Of these, the latter ten have been identified as having a carcinogenic or other toxic mature.
In light of this background, there is a need for new binder pitches which have reduced levels of PAH's, particularly those PAH's which are toxic. Such pitches would desirably retain the desirable physical characteristics of coal tar binder pitch, and be readily produced from abundant and readily available starting materials. The present invention addresses these needs.